1. Field of the Invention
The present invention relates to calibration for maintaining image quality.
2. Description of the Related Art
Image quality of an image formation apparatus varies depending on its use environment or use condition. Image quality also varies depending on the type of printing medium to be used. It is therefore necessary to change the image conversion conditions or image forming conditions depending on the environment or use condition (Japanese Patent Laid-Open No. 07-261479). It is also necessary to change the image conversion conditions or image forming conditions depending on the type of printing medium to be used (Japanese Patent Laid-Open No. 08-287217).
Japanese Patent Laid-Open No. 07-261479 assumes using a specific type of printing medium for calibration each time. For this reason, if the specific type of printing medium runs out, calibration cannot be performed. In Japanese Patent Laid-Open No. 08-287217 as well, to do calibration using an added arbitrary type of printing medium, a printing medium of the same type needs to be prepared each time. This is because the calibration is performed to maintain the gradation characteristic for the added arbitrary type of printing medium. If a printing medium of a type different from the designated type is used for calibration, for example, the amount of applied toner may be insufficient or exceed the permissible range designed for the image formation apparatus. This means that image quality cannot be maintained. It would be convenient for the operator if calibration for a desired printing medium can be performed using another type of printing medium. For example, to do calibration for maintaining the gradation characteristic for OHT (Overhead Transparency) sheets, using OHT sheets is designated. However, making plain paper usable for calibration to maintain the gradation characteristic for OHT sheets brings about significant advantages to the operator. The present invention proposes to register another type of printing medium in an image formation apparatus so that the other type of printing medium is usable in calibration to maintain image quality such as a gradation characteristic for a specific type of printing medium.
When a plurality of arbitrary types of printing media are registered for calibration, the calibration accuracy may change between these printing media. Especially, the calibration accuracy readily lowers when the other type of printing medium registered for calibration has characteristics largely different from those of a specific type of printing medium designated by the manufacturer in advance.